An interesting anecdote from an article off CNN.com --

Besides, picking that perfect pop song isn't as easy as it might sound, says Crowe, who has created iconic music moments in such movies as "Say Anything ..." and "Almost Famous." "You have to live and breathe it," he said. "You try to create that marriage and so often the record can overwhelm or be more eloquent than the movie."

The famous scene in "Say Anything ... ," in which John Cusack holds a stereo above his head outside Ione Skye's window and blares Peter Gabriel's "In Your Eyes," almost featured a different tune.

"That needed to be the perfect song. We even brought in a songwriter, a la Bacharach, to come in and write for that moment, and that really didn't work," he said in an interview. "Nothing worked but that song. It was written in the script to be a Billy Idol song, 'To Be a Lover.' It was the week that I liked that song."

But then when it came time to film that scene, he realized the upbeat Idol tune wouldn't work. ("Cusack wanted Fishbone -- 'I wanna play Fishbone!' " Crowe added, saying that the actor is actually playing that band's "Party at Ground Zero" while shooting this wistful moment.)

"We tried every possible song. Then I was driving to the editing room one day and I had the wedding mix from my wedding in my car. I was listening to stuff on it, it brought back memories, then 'In Your Eyes' comes on. 'I drive off in my car!' " he gushed, quoting Gabriel's lyrics. "It's a song about instincts! I put the pedal to the floor and we put it in the scene and it worked. Then we had to try to get the song, which is its own crusade and a really difficult thing."

Nice anecdote. I found what I've been looking for too, the song that John actually played during the boombox scene:

Fishbone - Party at Ground Zero
http://www.youtube.com/watch?v=vrONIb9gQ-k

In Your Eyes was really the perfect pick